The present invention relates to a range finder system using superimposed two images.
Conventional range finder system is provided with, for example, a first and a second windows arranged spaced apart from each other by a predetermined base line length. Light beams entered through the first and second windows are combined by a beam combiner such as a half mirror and then directed into a common eyepiece optical system. A photographer observes the dual image, which is formed by superimposing two images respectively corresponding to the first and second windows, of an object through the eyepiece optical system. A rotatable mirror is provided between the second window and the half mirror to vary the degree of coincidence of the superimposed two images in the direction of the base line, and a distance to the object is determined based on the angle of rotation of the rotatable mirror at which the two superimposed images of the object coincide.
In an interlocking type range finder, movement of a photographing lens is interlocked with the rotation of the rotatable mirror such that the photographing lens is brought into an in-focus position when the rotation angle of the rotatable mirror is adjusted and the superimposed images coincide.
Since the above-described range finder requires an optical path running from the first window to the eyepiece, and another optical path running from the second window to the half mirror and then to the eyepiece, a relatively large space is required which prevents cameras from being made compact. Further, in order to improve measurement accuracy in range finding, the base length needs to be sufficiently long, and a space for accommodating the optical path between the first and second windows becomes large.